/*
 * SHA1 Wikipedia Page: http://en.wikipedia.org/wiki/SHA-1
 *
 * Copyright (c) 2012-22 SAURAV MOHAPATRA <mohaps@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/**
 * \file TinySHA1.hpp
 * \author SAURAV MOHAPATRA <mohaps@gmail.com>
 * \date 2012-22
 * \brief TinySHA1 - a header only implementation of the SHA1 algorithm in C++. Based
 * on the implementation in boost::uuid::details.
 *
 * In this file are defined:
 * - sha1::SHA1
 */
#ifndef _TINY_SHA1_HPP_
#define _TINY_SHA1_HPP_
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <stdint.h>

/**
 * \namespace sha1
 * \brief Here is defined the SHA1 class
 */
namespace sha1
{
    /**
     * \class SHA1
     * \brief A tiny SHA1 algorithm implementation used internally in the
     * Crow server (specifically in crow/websocket.h).
     */
    class SHA1
    {
    public:
        typedef uint32_t digest32_t[5];
        typedef uint8_t digest8_t[20];
        inline static uint32_t LeftRotate(uint32_t value, size_t count) {
            return (value << count) ^ (value >> (32-count));
        }
        SHA1(){ reset(); }
        virtual ~SHA1() {}
        SHA1(const SHA1& s) { *this = s; }
        const SHA1& operator = (const SHA1& s) {
            memcpy(m_digest, s.m_digest, 5 * sizeof(uint32_t));
            memcpy(m_block, s.m_block, 64);
            m_blockByteIndex = s.m_blockByteIndex;
            m_byteCount = s.m_byteCount;
            return *this;
        }
        SHA1& reset() {
            m_digest[0] = 0x67452301;
            m_digest[1] = 0xEFCDAB89;
            m_digest[2] = 0x98BADCFE;
            m_digest[3] = 0x10325476;
            m_digest[4] = 0xC3D2E1F0;
            m_blockByteIndex = 0;
            m_byteCount = 0;
            return *this;
        }
        SHA1& processByte(uint8_t octet) {
            this->m_block[this->m_blockByteIndex++] = octet;
            ++this->m_byteCount;
            if(m_blockByteIndex == 64) {
                this->m_blockByteIndex = 0;
                processBlock();
            }
            return *this;
        }
        SHA1& processBlock(const void* const start, const void* const end) {
            const uint8_t* begin = static_cast<const uint8_t*>(start);
            const uint8_t* finish = static_cast<const uint8_t*>(end);
            while(begin != finish) {
                processByte(*begin);
                begin++;
            }
            return *this;
        }
        SHA1& processBytes(const void* const data, size_t len) {
            const uint8_t* block = static_cast<const uint8_t*>(data);
            processBlock(block, block + len);
            return *this;
        }
        const uint32_t* getDigest(digest32_t digest) {
            size_t bitCount = this->m_byteCount * 8;
            processByte(0x80);
            if (this->m_blockByteIndex > 56) {
                while (m_blockByteIndex != 0) {
                    processByte(0);
                }
                while (m_blockByteIndex < 56) {
                    processByte(0);
                }
            } else {
                while (m_blockByteIndex < 56) {
                    processByte(0);
                }
            }
            processByte(0);
            processByte(0);
            processByte(0);
            processByte(0);
            processByte( static_cast<unsigned char>((bitCount>>24) & 0xFF));
            processByte( static_cast<unsigned char>((bitCount>>16) & 0xFF));
            processByte( static_cast<unsigned char>((bitCount>>8 ) & 0xFF));
            processByte( static_cast<unsigned char>((bitCount)     & 0xFF));

            memcpy(digest, m_digest, 5 * sizeof(uint32_t));
            return digest;
        }
        const uint8_t* getDigestBytes(digest8_t digest) {
            digest32_t d32;
            getDigest(d32);
            size_t di = 0;
            digest[di++] = ((d32[0] >> 24) & 0xFF);
            digest[di++] = ((d32[0] >> 16) & 0xFF);
            digest[di++] = ((d32[0] >> 8) & 0xFF);
            digest[di++] = ((d32[0]) & 0xFF);

            digest[di++] = ((d32[1] >> 24) & 0xFF);
            digest[di++] = ((d32[1] >> 16) & 0xFF);
            digest[di++] = ((d32[1] >> 8) & 0xFF);
            digest[di++] = ((d32[1]) & 0xFF);

            digest[di++] = ((d32[2] >> 24) & 0xFF);
            digest[di++] = ((d32[2] >> 16) & 0xFF);
            digest[di++] = ((d32[2] >> 8) & 0xFF);
            digest[di++] = ((d32[2]) & 0xFF);

            digest[di++] = ((d32[3] >> 24) & 0xFF);
            digest[di++] = ((d32[3] >> 16) & 0xFF);
            digest[di++] = ((d32[3] >> 8) & 0xFF);
            digest[di++] = ((d32[3]) & 0xFF);

            digest[di++] = ((d32[4] >> 24) & 0xFF);
            digest[di++] = ((d32[4] >> 16) & 0xFF);
            digest[di++] = ((d32[4] >> 8) & 0xFF);
            digest[di++] = ((d32[4]) & 0xFF);
            return digest;
        }

    protected:
        void processBlock() {
            uint32_t w[80];
            for (size_t i = 0; i < 16; i++) {
                w[i]  = (m_block[i*4 + 0] << 24);
                w[i] |= (m_block[i*4 + 1] << 16);
                w[i] |= (m_block[i*4 + 2] << 8);
                w[i] |= (m_block[i*4 + 3]);
            }
            for (size_t i = 16; i < 80; i++) {
                w[i] = LeftRotate((w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16]), 1);
            }

            uint32_t a = m_digest[0];
            uint32_t b = m_digest[1];
            uint32_t c = m_digest[2];
            uint32_t d = m_digest[3];
            uint32_t e = m_digest[4];

            for (std::size_t i=0; i<80; ++i) {
                uint32_t f = 0;
                uint32_t k = 0;

                if (i<20) {
                    f = (b & c) | (~b & d);
                    k = 0x5A827999;
                } else if (i<40) {
                    f = b ^ c ^ d;
                    k = 0x6ED9EBA1;
                } else if (i<60) {
                    f = (b & c) | (b & d) | (c & d);
                    k = 0x8F1BBCDC;
                } else {
                    f = b ^ c ^ d;
                    k = 0xCA62C1D6;
                }
                uint32_t temp = LeftRotate(a, 5) + f + e + k + w[i];
                e = d;
                d = c;
                c = LeftRotate(b, 30);
                b = a;
                a = temp;
            }

            m_digest[0] += a;
            m_digest[1] += b;
            m_digest[2] += c;
            m_digest[3] += d;
            m_digest[4] += e;
        }
    private:
        digest32_t m_digest;
        uint8_t m_block[64];
        size_t m_blockByteIndex;
        size_t m_byteCount;
    };
}
#endif
